In recent years, there have been often used various resin compositions curable with an active energy ray in coatings or inks, or as a sealing material, as a resist material, as a material for forming a protective film or as a material for forming a pattern. As such resin compositions, for use in forming a protective film for printed wiring board or for use as a resist material for forming a wiring pattern therefor, there are known, for example, a dry film resist containing a high molecular material capable of forming a film under the trade name of RISTON (produced by Du Pont Japan Ltd.) and a thick film liquid resist according to photographic method under the trade name of PROBIMER (produced by Ciba Geigy Co.).
These known resin compositions comprise mainly (a) high molecular materials contributing to formation of a film or a dry coating and (b) a material curable with an active energy ray. And for these resin compositions, their adhesiveness with a substrate, their developing properties for the formation of a pattern, their durability, painting property and drying property as a paint film are varied depending upon the kinds and the molecular structures of said high molecular materials (a). Therefore, when such resin composition is used aiming at providing the above properties as desired, the kinds of the high molecular materials (a) and the molecular design among the components are properly determined so as to meet the requirements.
However, any of the known resin compositions curable with an active energy is still not sufficient in view of the adhesiveness with various substrates even in the case where it is so designed in the above way.
In order to solve this problem, there have been made proposals to add an auxiliary capable of forming a complex with a metal such as a specific heterocyclic compound or a coupling agent to such resin composition, whereby improving its adhesiveness with a metallic substrate as disclosed in Japanese Laid-open Patent Applications No. 5934/1976 and No. 24035/1983.
However, there is still an unsolved problem in the case of any of these proposals, that the additive will cause oxidation or corrosion on the resin composition after the lapse of time.
Other than the above proposals, there has been proposed a high molecular material comprising a graft copolymerized polymer having polar groups on its graft chains aiming at obtaining a cured composition exhibiting a sufficient adhesiveness with a substrate without addition of such additive as mentioned above by Japanese Laid-open Patent Application No. 283645/1986. The resin composition curable with an active energy ray containing said high molecular material to be provided by this publication is such that it makes it possible to realize an improvement in the adhesiveness of the resulting paint film with a substrate and also in its durability without using such additive as mentioned above. However, even for such resin composition as described in the above publication, there still remains the unsolved problem of how to determine the molecular structures for the high molecular weight materials to be used in preparing resins having the desired properties. In fact, in general, it is technically difficult to synthesize a desirable graft copolymerized polymer so that it has a predetermined molecular weight and a predetermined content for the graft chains and it has a desired weight average molecular weight in the range from 50,000 to 350,000.
In order to provide desired enhancement in the developing properties upon formation of a pattern, in other words, in the dissolving rate of unpolymerized part, the swelling of polymerized part, the sensitivity as a result of these factors, the sharpness of the resulting pattern and the controlling ability of the resolution, it is necessary for the number average molecular weight of the high molecular material involved to be not excessively small. In the case of a graft copolymerized polymer, to connect a plurality of graft chains having a length sufficient enough to provide an effective adhesiveness with its trunk chain of a relatively large molecular weight to thereby make the resulting graft copolymerized polymer to have a desired number average molecular weight is generally recognized as being difficult because of steric hindrance in this technical field.
In the case where the number average molecular weight of the high molecular material involved is excessively small, when a pattern is formed using such high molecular material, there are limits for the developing properties, that is, the dissolving rate of unpolymerized part, the swelling of polymerized part, the sensitivity as a result of these factors, the sharpness of the resulting pattern and the controlling allowance of the resolution.